Thread pitches on small parts.

Hello Dave,

If you have , an old fashioned, slide projector mount your threaded plunger in the plane where the slide normally goes and you can have a wide range of magnifications.

You can check the magnification by first using a drill shank, which is easily measured accurately, as the object.

Regards John

I often scale things from digital photos. Prop the part up with some Blu Tack and put a steel rule close to it at the same height as the centreline (so as to place both in the same plane. Take the best image you can (with a macro focus option if available), and scale it up to fill your monitor. Then measure on the screen the screw pitch and the steel rule - use a plastic ruler to avoid scratching the screen. Apply the scale ratio from the photo to the component, i.e.

Pitch = real inches x photo pitch / photo inches

or

Pitch = real mm x photo pitch / photo mm

You can do the same thing (upside down) using a scanner, I used to do this to check plastic extrusions in the absence of a shadowgraph.

Brian

Just as a matter of interest, good info from Long Island Dial Indicators on tip standards here

**LINK**

So apparently, according to the third paragraph there, standard tip threads are either UN 4-48 or M 2.5, but deliberately made undersize so that if the threaded section breaks off inside the plunger, it can be easily removed. I guess it relies on the shoulder on the tip to hold it firm, not the thread, similar to how a lathe chuck is located on screw-on spindles.

It's a great site they have there at Long Island, well worth browsing around for a while.

Edited By Hopper on 12/06/2016 08:50:28

deja vu

As Hopper says, half way down page 1, you have the correct measurement tool in your hands. I don't see the need for CFEs, thread gauges etc. Only difference is I would try to make more turns of the tip - looks as if 4 or 5 turns may be possible. This would reduce the measurement error.

This looks like a mountain out of a molehill. You could have measured it within a few minutes. Given that it's almost certainly metric (ie not made in the US), it will surely be a simple matter to try a screw in the shaft or a nut on the tip. Start with an M2.5?

The only small screws i have laying around are from computers, so nothing as low as a 2.5, On mine you cannot get 4 or 5 turns. 3 turns and it falls out. A very sloppy fit also.

I have an M2 0.4 tap and screws for something else and they are too small.

My phones no good on macro, wont focus properly. Silly because teh previous model was brill for macro.

Will have to try the scanner. Thread pitches and cheap items from China always seem to test me, M6, M7 and even an M8 at 0.75 pitch for example. Switches and potentiometers arrived without fixing nuts and these sizes, find suitable nuts was a pain in the whatsit.

Got any indexable tools? the torx screws on teh smaller ones of those are often M2.5

Got the microscope out and found a bit of an issue... This is supposed to be a 0.45 gauge.

9 more of these in my Thread Gauge album, all from the 0.45 gauge, but the 0.35 and 0.4 are much the same.

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Pitch i mean, but you knew that      Editing my typo's could be a full time job for you 

The hours are long and the pay is non existent though.

Edited By Dave Smith the 16th on 13/06/2016 00:58:14

This played on my mind for some reason and nope i was right, its a 0.45 thread pitch gauge

So its a 0.45 gauge it gauges 0.45 threads, well this one wont

Sorry, Dave ...

The 'zipped' smiley was a bit cryptic : I was trying to skip lightly over the inevitable discussion about fitness-for-purpose, etc.

What I was trying to convey was something along the lines of : "If that's supposed to be a thread gauge, no wonder you're having trouble" ... [expressed as "no comment"].

MichaelG.

That gauge probably matches the quality of the screw thread quite well

A delightful digression here: **LINK**

SEM images of a fine screw thread.

MichaelG.

Never mind its all lost on me

Jason B, I didnt think of that. Just had a quick look and the threads on the screw look much better. I will pop it under the scope later for a proper look. How do you hold a gauge and a screw close to each other and on the same level? I couldn't think howto do it.

Thanks

Edited By Dave Smith the 16th on 13/06/2016 16:18:32

I usually just hold them upto a light fitting and eyeball it.

Your eyesight must be better than mine I couldnt do that with the 0.4 or 0.45 pitch screws side by side.

I need something to enlarge them. Age creeping up on me

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